The invention is based on patent application Nos. 2000-22973 Pat., 2000-22993 Pat., 2000-23003 Pat., and 2000-23039 Pat.filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image display method, an image forming apparatus and a reversible image display method, and particularly relates to an image display method utilizing a reversible image display medium, an image forming apparatus utilizing a reversible image display medium and a reversible image display medium in which image displaying and image erasing operations can be repeated.
2. Description of the Background Art
At present, image display is performed, e.g., in the following manners. A person uses a pencil, a pen, paints or the like, and manually writes or draws characters, pictures or the like on an image display medium such as paper sheet. Also, a computer, a word processor or the like is used to display text, graphics or the like on a display such as a CRT display, or output them on a medium such as a paper sheet via a printer for display.
A copying machine or the like may be used for producing duplication, on a medium of paper or the like, of the texts, pictures, graphics or the like, which are produced on the medium of paper or the like by a person or by a printer. A facsimile machine may be used for sending such contents (texts, pictures graphics and others) prepared in the above manner for producing duplication on another medium of paper or the like.
The above image display, which is performed to display the texts, pictures or the like on the image display medium of paper or the like by a pencil, pen or the like, or by an image forming apparatus such as a printer, a copying machine or a facsimile machine operating in a electrophotographic method, an ink-jet method, a heat transfer method or the like, can achieve clear image display in a high resolution, and thus can achieve easy-on-the-eyes display.
However, it is impossible to repeat display and erasure of the images on the image display medium of paper or the like. In the case where the paper is used for writing characters or the like by a pencil, the characters can be erased by an eraser to a certain extent. However, it is difficult to erase completely the characters or the like written in an ordinary density, although it may be possible when written in a light density. The medium of paper or the like cannot be reused except for the case of using the rear surface of the medium, which is not yet used for the image display.
Accordingly, the medium of paper or the like bearing images will be abandoned or burnt when it is not longer required. This results in consumption of a large mount of resources. The printer, copying machine or the like also consume consumable products or materials such toner or ink. For obtaining the new display medium of paper or the like as well as toner, ink or the like, energies and resources are required for producing them. This is contrary to the current demand for reduction in environmental loads.
In contrast to the above, the image display by a display such as a CRT display can repeat the image display and the image erasure. However, the resolution, clarity and precision of images are restricted, as compared with the images displayed by the printer or the like on the paper medium or the like. Due to the relatively low resolution and the light emission from the display, operations for a long time are likely to be hard to eyes.
Electrophoretic display has been proposed as an image display method allowing repetition of the image display and image erasure. In the electrophoretic display method, two substrates including at least one transparent substrate are opposed together with a spacer therebetween to form a closed space therebetween, and the space is filled with a display liquid formed of a dispersion medium and electrophoretic particles, which are dispersed in the dispersion medium and are different in color from the medium. The image display is performed by an application of an electrostatic field and in a color of the particles or a color of the dispersion medium.
The display liquid is usually formed of isoparaffin-contained dispersion medium, particles of titanium dioxide or the like, dyes applying contrast in color to the particles, and an additive such as a surface active agent, or a charge applying agent.
In the electrophoretic display, the display is performed by utilizing contrast between particles of a high refractive index (e.g., titanium dioxide particles) and colored insulating liquid, and therefore the particles cannot hide the colored liquid to a high extent, resulting in a low contrast. Further, settling and condensation of particles are liable to occur due to a very large difference in specific gravity between the particles and the dispersion medium in the display liquid. This is liable to lower the display contrast. Further, it is difficult to display the images with high stability for a long time, and remaining of former images is liable to occur. Further, the degree of charging of the particles in the liquid significantly changes with time, which also impairs the stability of the image display.
Accordingly, an object of the invention is to provide an image display method, which allows repeating of image display and image erasure, and thereby can reduce consumption of image display media of paper or the like relating to the conventional image display and consumable materials such as developer and ink so that a current demand for reduction in environmental loads can be satisfied.
Another object of the invention is to provide an image display method, which allows display of images in good contrast and high quality.
Still another object of the invention is to provide an image display method, which allows display of images in high resolution and high quality.
Yet another object of the invention is to provide an image display method, which allows stable display of high-quality images for a long time.
Further another object of the invention is to provide an image display method, which can suppress remaining of former images, and therefore can exhibit good reversibility so that images of good quality can be displayed.
A further another object of the invention is to provide an image display method, which can reduce a drive voltage required for image display.
A further object of the invention is to provide an image forming apparatus used for at least one of such image display methods.
A further object of the invention is to provide a reversible image display medium, which allows repeating of image display and image erasure.
The invention provides image display methods, image forming apparatuses and reversible (in other words, reusable) image display mediums described below.
(1) First Image Display Method and Image Forming Apparatus Implementing the Same
(1-1) First Image Display Method
An image display method including the steps of:
preparing a reversible image display medium including:
two sheets opposed to each other with a predetermined gap therebetween;
one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and
dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other;
displaying an image by forming a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby moving the developer particles, with the developer particles in each of the cell(s) being in the frictionally charged state; and
stirring the developer in the reversible image display medium in the image display step.
(1-2) Image Forming Apparatus for Implementing First Image Display Method
An image forming apparatus for forming an image on a reversible image display medium including two sheets opposed to each other with a predetermined gap therebetween; one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and being in a frictionally charged state, including;
an electric field forming device for forming a predetermined electrostatic field for each pixel in accordane with the image to be displayed and thereby moving the developer particles to display the image, with the developer particles in each of the cell(s) being in the frictionally charged state; and
a stirring device for stirring the developer in the reversible image display medium, wherein
the electric field forming device includes an electrostatic latent image forming device for forming an electrostatic latent image corresponding to the image to be formed on an outer surface of one of the two sheets of the reversible image display medium, and the electrostatic field can be formed based on the electrostatic latent image formed by the electrostatic latent image forming device simultaneously with or after the formation of the electrostatic latent image, and
the stirring device is opposed to a portion of a reversible image display medium transporting path in or upstream to the electrostatic field forming region of the electric field forming device in the relative transporting direction of the reversible image display medium with respect to the electric field forming device.
(2) Second Image Display Method and Image Forming Apparatus Implementing the Same
(2-1) Second Image Display Method
An image display method corresponding to the first image display method except for that the reversible image display medium includes an electrode formed on an inner surface of one of the sheets, and an electrode formed on an inner surface of the other sheet and opposed to the electrode; the image display step is performed by applying a voltage across the opposite electrodes to form the electrostatic field; and the stirring of the developer is performed before or simultaneously with the formation of the electrostatic field.
(2-2) Image Forming Apparatus for Implementing Second Image Display Method
An image forming apparatus for forming an image on a reversible image display medium including two sheets opposed to each other with a predetermined gap therebetween; one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; dry developer contained in each of the cell(s); an electrode formed on an inner surface of one of the sheets; and an electrode formed on an inner surface of the other sheet and opposed to the electrode, the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other, including;
an electric field forming device for forming a predetermined electrostatic field for each pixel in accordane with the image to be displayed by applying a voltage across the opposite electrodes and thereby moving the developer particles to display the image; and
a stirring device for stirring the developer in the reversible image display medium, wherein
the stirring device is opposed to a portion of a reversible image display medium transporting path in or upstream to the electrostatic field forming region of the electric field forming device in the relative transporting direction of the reversible image display medium with respect to the electric field forming device.
(3) Third Image Display Method and Image Forming Apparatus Implementing the Same
(3-1) Third Image Display Method
An image display method including the steps of:
preparing a reversible image display medium including:
two sheets opposed to each other with a predetermined gap therebetween;
one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and
dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other;
displaying an image by forming a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby moving the developer particles, with the developer particles in each of the cell(s) being in the frictionally charged state; and
performing image erasing processing on the reversible image display medium prior to the image display step.
(3-2) Image Forming Apparatus for Implementing Third Image Display Method
An image forming apparatus for forming an image on a reversible image display medium including two sheets opposed to each other with a predetermined gap therebetween; one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other, including;
an electric field forming device for forming a predetermined electrostatic field for each pixel in accordane with the image to be displayed and thereby moving the developer particles to display the image, with the developer particles in each of the cell(s) being in the frictionally charged state; and
an image erasing device for performing image erasing processing on the reversible image display medium, the image erasing device being opposed to a portion of a reversible image display medium transporting path upstream to the electric field forming device in the relative transporting direction of the reversible image display medium with respect to the electric field forming device.
(4) Fourth Image Display Method
An image display method including the steps of:
preparing a reversible image display medium including:
two sheets opposed to each other with a predetermined gap therebetween;
one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and
dry developer contained in each of the cell(s),
the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other; and
displaying an image by forming a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby moving the developer particles, with the developer particles in each of the cell(s) being in the frictionally charged state, wherein
the electrostatic field formed in the image display step is formed based on an electrostatic latent image formed in accordance with the image to be displayed on an outer surface of one of the two sheets.
(5) Fifth Image Display Method
An image display method including the steps of: preparing a reversible image display medium including:
two sheets opposed to each other with a predetermined gap therebetween;
one or more developer accommodating cells formed between the two sheets, and each having a periphery surrounded by a partition wall; and
dry developer contained in each of the cell(s),
the dry developer containing at least two kinds of frictionally chargeable dry developer particles having different chargeable polarities and different optical reflection densities, and
at least two kinds of the dry developer particles forming the dry developer within the developer accommodating cell(s) being frictionally charged to have the charged polarities different from each other;
uniformly charging a sheet surface of the reversible image display medium to a predetermined potential; and
displaying an image by forming an electrostatic latent image corresponding to the image to be displayed on the sheet surface charged in the charging step, and forming, based on the electrostatic latent image, a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby moving the developer particles to display the image.
(6) Sixth Image Display Method
An image display method including the steps of:
preparing a reversible image display medium including insulating liquid of a predetermined color, charged developer particles exhibiting a color different from the color of the insulating liquid and dispersed in the liquid, and two sheets opposed to each other with a predetermined gap therebetween, the insulating liquid and the charged developer particles being confined between the two sheets;
uniformly charging a sheet surface of the reversible image display medium to a predetermined potential; and
displaying an image by forming an electrostatic latent image corresponding to the image to be displayed on the sheet surface charged in the charging step, and forming, based on the electrostatic latent image, a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby moving the charged developer particles to display the image.
(7) Seventh Image Display Method
An image display method including the steps of:
preparing a reversible image display medium including spherical developer particles each having an outer surface formed of halves being different in color and amount of absorbable ions from each other, surrounded by an insulating liquid layer, respectively, and buried in an insulating property holding medium;
uniformly charging a sheet surface of the reversible image display medium to a predetermined potential; and
displaying an image by forming an electrostatic latent image corresponding to the image to be displayed on the medium surface charged in the charging step, and controlling the directions of the surfaces of the different colors of the spherical developer particles by forming, based on the electrostatic latent image, a predetermined electrostatic field for each pixel in accordance with the image to be displayed.
(8) Eighth Reversible Image Display Medium
A reversible image display medium, wherein spherical developer particles each having an outer surface formed of halves being different in color and amount of absorbable ions from each other are surrounded by an insulating liquid layer,respectively, and are buried in an insulating property holding medium.
According to this medium, the image display can be performed by forming a predetermined electrostatic field for each pixel in accordance with the image to be displayed and thereby inverting or rotating the spherical developer particles. Naturally, the seventh image display method may be employed for image display on this medium.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.